The present invention relates generally to a method for continuous color mapping of nonscalar data. Moreover, the method for continuous color mapping of non-scalar data comprises mapping both single component and multicomponent nonscalar data whereby the single component and multicomponent nonscalar data can be uniquely displayed separately or combined, by chromatic vector addition, and uniquely displayed concurrently. More particularly, the present invention provides a method for producing separate continuous color displays of seismic data as well as a method for combining multiple sets of seismic data, by chromatic vector addition, to uniquely display two or more sets of seismic data concurrently.
Color mapping of data involves a series of transformations employing a color coordinate system. Most color mappings of scalar data are produced by varying shades of a selected color or by mixing selected combinations of primary colors (e.g., red, green and blue). Exemplary of a color coordinate system which employs such an approach is the RGB (red, green, and blue) Cartesian coordinate system where the three colors (red, green, and blue) define three color axes (R,G,B). In the RGB color coordinate system, each color has an intensity or saturation ranging from no color to maximum color (e.g., from 0 to 1) wherein the intensity or saturation of the selected color can be varied according to scaled values of the data to be displayed. As a result, separate sets of scalar data can be displayed employing the RGB color coordinate system shown in FIG. 1. By way of example, the following ordered (R,G,B) sets can produce an RGB color cube representing the following colors:
(0,0,0)=Black PA1 (1,1,1)=White PA1 (1,0,0)=Red PA1 (0,1,0)=Green PA1 (0,0,1)=Blue PA1 (1,1,0)=Yellow PA1 (0,1,1)=Cyan PA1 (1,0,1)=Magenta
(where 0 indicates absence of primary color; and 1 indicates presence of primary color).
Alternative color coordinate systems for transforming scalar data are also available and generally compromise variations of the HLS (hue, lightness, saturation) system. With the RGB system, as with any other color coordinate system, a simple transformation for displaying scalar data can be expressed by: EQU U.sub.i =a+bx.sub.i ( 1)
where U.sub.i is a transform of the scalar data x.sub.i, a is an offset to ensure a minimum value of U.sub.i =0, and b is a scaling factor such that U.sub.i has a maximum value of 1.
Unfortunately, real data sets are not always limited to scalar data sets or data sets for which it is informative to represent both positive and negative values as scalar data by use of an offset. Exemplary of such real data are seismic traces recorded during geophysical exploration which represent the earth's response to seismic energy imparted therein. Seismic traces represent one-dimensional data and are generally depicted in either the time-domain or frequency domain. Such seismic traces are complex sinusoids having both positive and negative values. To more accurately interpret such seismic traces, knowledge of more than scalar values is needed. The difficulty in categorizing both the positive and negative measures of seismic traces has resulted in color systems which generally assign colors only to positive values of the seismic trace. Such a coloring system is decidedly biased or aliased in its representation of the complete seismic trace. Other color transformation schemes, such as described by Shock, et al., in U.S. Pat. No. 4,661,935, have been proposed to more accurately portray seismic data. However, the Shock, et al., scheme neither provides a mechanism for uniquely displaying nonscalar data using less than four colors nor a mechanism for combining two or more separate sets of nonscalar data into a single display. The present invention provides a method for continuous color displays of both one-dimensional and multidimensional data sets which overcome the aforementioned limitations.